A fight played out last month at San Francisco's Board of Permit Appeals that was a perfect microcosm of why the city has a housing shortage: It demonstrated an aversion to new housing, coupled with an expensive planning process, topped off with arbitrary decisions.

Exhibit A: 1050 Valencia St., a former Kentucky Fried Chicken store. After a process lasting nearly a decade, the city adopted the Eastern Neighborhoods Plan, which rezoned the eastern third of San Francisco. The plan's policy goals were to increase housing density near transit and to deliver more affordable housing. The 1050 Valencia site is part of that plan area.

The developer proposed a project fully within that zoning and said he would build the required two affordable units on-site. The project would have no parking, as it is close to transit. Over the six-year process leading to approval, the developer agreed to reduce the number of units from 16 to 12 and to add car sharing. The Planning Commission approved the project over objections by some neighbors and the adjacent Marsh theater, and the Board of Supervisors rejected an environmental appeal.

Project opponents then appealed to the Board of Permit Appeals, which - citing no policy basis for its decision - arbitrarily chopped off the top story of the building. That decision reduced the number of units from 12 to nine and thus eliminated the two affordable units, because 10 units is the threshold triggering affordable-unit requirements. Welcome to housing policy in San Francisco: a policy based not so much on our city's dire housing needs but on who can turn out the most people at a public hearing.

This case-by-case decision-making process undermines all forms of housing, both affordable and market rate. Indeed, affordable housing projects are much less able to weather the time, cost and energy required to move a project through San Francisco's approval gantlet.

San Francisco is experiencing a housing crisis. One-bedroom apartments are going for $3,000 a month or more. The pressures of this market lead to displacement, including Ellis Act evictions, make it hard for working-class people to live here, and make raising a family here nearly impossible.

Yet this crisis didn't just happen. San Francisco has been unwilling to prioritize smart housing production of market-rate and affordable units, even while our laws state that housing is to be encouraged.

Over the past 10 years, San Francisco's population has grown by 75,000 people. Over the same time period, our city produced 17,000 units of housing. You do the math: Over the next 25 years, San Francisco is projected to add another 150,000 residents. If we continue to produce housing at the same anemic rate, $3,000 rents will begin to look cheap.

This disconnect - saying that we need more housing while arbitrarily finding reasons to kill or water down projects that provide that housing - is having profound effects on our city and its beautiful diversity, economic and otherwise.

I'm certainly not suggesting that the 1050 Valencia project and the loss of its two affordable and one market-rate units is going to move San Francisco's housing market. Yet, the dynamics that led to this decision, exacerbated as many 1050 Valencia projects have navigated the process over the years, have had significant effects over time. We can't keep saying we want to save the forest, while continuing to chop down trees. It's incumbent on all of us to make sure policymakers understand that they must keep the big housing picture in mind rather than make ad hoc decisions disconnected from the housing crisis we face.